Impelement owner references

[damyan]

Currently the connections between networks, subnets and IPs are implemented through labels. Please use owner references instead.

Note: due to missing owner refs the ipamctl move command currently fails with

Operation cannot be fulfilled on ips.ipam.metal.ironcore.dev "020211571157-static-master-1": the object has been modified; please apply your changes to the latest version and try again
clean up of CRs was performed to restore a target cluster's state with error result: admission webhook "vnetwork.kb.io" denied the request: Network.ipam.metal.ironcore.dev "oob" is invalid: metadata.name: Internal error: Network has active IPv4 subnets```